Now zoologist Louise Shilton has turned detective in an attempt to discover where the fruit bats have gone and exactly why they fled.

Shilton, who works for Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) in Atherton, says that the bats' numbers for this time of year are as much as a third lower than they have been in previous years.

"I've heard numerous reports from residents who were holed up in their properties near well-known [flying fox] camps," Shilton said.

"They said [the bats] took flight en masse at three o'clock on the Sunday afternoon," the day before the cyclone hit the mainland.

Normally animals fleeing an unusual weather event can sense a drop in air pressure and head toward a safe area further inland, Shilton says.

But on this occasion the flying foxes acted out of character.

"The foxes took flight, and the really peculiar thing is they headed toward the cyclone, toward the coast," she said

Another peculiar phenomenon happened about a week after Larry, when large numbers of flying foxes were also spotted leaving their camps about three months earlier than they would normally begin their winter migration.

Scientists estimate the region is missing tens of thousands of the bats, and no one is sure why.